The present invention relates to an immobilized lipase or phospholipase which is suitable for transesterification of oils and fats or phospholipids, a process for producing it and a process for transesterifying oils and fats or phospholipids with the immobilized lipase or phospholipase.
The transesterification reaction is an important means for the production of wax esters, fatty acid esters, saccharide esters, steroids and the like or for modifying vegetable oils and animal oils. When a lipase which is an enzyme for decomposing oils and fats is used as a catalyst in the transesterification reaction, this reaction can be conducted under mild conditions and, in addition, the intended product can be efficiently produced according to the substrate specificity and site specificity thereof. It was proposed to conduct the transesterification reaction in the presence of a lipase in an amount sufficient for expressing the enzymatic activity while water content of the reaction system is reduced as far as possible. However, it is difficult to homogeneously disperse the lipase in a system containing very small amount of water (oily system), since lipase is soluble in water.
To solve this problem, an immobilized lipase comprising a lipase carred on an insoluble carrier is used. By employing the immobilized lipase, there can be obtained advantages in that the separation of the product is further facilitated, the repeated use of the lipase is made possible and the continuation of the reaction is also facilitated.
However, although the immobilized lipase has the above-described advantages, no immobilized lipase which is practically usable has been obtained.
Carriers heretofore proposed for the production of the immobilized lipase include porous chitosan moldings [Japanese Patent Unexamined Published Application (hereinafter referred to as "J.P. KOKAI") No. 59-213390], macroporous anion exchange resins (J.P. KOKAI No. 60-98984), macroporous phenolic adsorbent resins (J.P. KOKAI No. 61-20268), animal bones (J.P. KOKAI No. 64-80286), products obtained by baking foaming phenolic resins (J.P. KOKAI No. 2-100678), hydrophobic carriers having pore diameter of at least 50 nm (J.P. KOKAI No. 2-138986), cation exchange resins (J.P. KOKAI No. 3-64185) and macroporous acrylic adsorbent resins (J.P. KOKAI No. 3-501922). However, a sufficient lipase activity cannot be obtained by using such a carrier. J.P. KOKAI No. 60-137290 discloses a process for immobilizing an enzyme on a polysaccharide carrier by means of an aldehyde group formed by oxidation of a hydroxyl group of the polysaccharide. However, this process is unsuitable for reactions in a system containing very small amount of water, since the carrier is hydrophilic. Although a process for immobilizing an enzyme on a chelate resin is disclosed in J.P. KOKAI No. 1-262795, an activity sufficient for the practical use has not yet been obtained.